Chemical mechanical polishing composition and method for polishing phase change alloys

ABSTRACT

A method for chemical mechanical polishing of a substrate comprising a germanium-antimony-tellurium chalcogenide phase change alloy (GST) using a chemical mechanical polishing composition comprising, as initial components: water; an abrasive; at least one of a phthalic acid, a phthalic anhydride, a phthalate compound and a phthalic acid derivative; a chelating agent; a poly(acrylic acid-co-maleic acid); and an oxidizing agent; wherein the chemical mechanical polishing composition facilitates a high GST removal rate with low defectivity.

The present invention relates to a chemical mechanical polishingcomposition and methods of using the same. More particularly, thepresent invention relates to a chemical mechanical polishing compositionfor polishing a substrate having a germanium-antimony-tellurium phasechange alloy.

Phase change random access memory (PRAM) devices that use phase changematerials that can be electrically transitioned between an insulating,generally amorphous state and a conductive, generally crystalline statehave become a leading candidate for the next generation of memorydevices. These next generation PRAM devices may replace conventionalsolid state memory devices such as dynamic random accessmemory—DRAM—devices; static random access memory—SRAM—devices, erasableprogrammable read only memory—EPROM—devices, and electrically erasableprogrammable read only memory—EEPROM—devices that employ microelectroniccircuit elements for each memory bit. These conventional solid statememory devices consume a lot of chip space to store information, thuslimiting chip density; and are also relatively slow to program.

Phase change materials useful in PRAM devices include chalcogenidematerials such as, germanium-tellurium (Ge—Te) andgermanium-antimony-tellurium (Ge—Sb—Te) phase change alloys. Themanufacture of PRAM devices include chemical mechanical polishing stepsin which chalcogenide phase change materials are selectively removed andthe device surface is planarized.

Tellurium tends to be relatively mobile in chalcogenide phase changealloy films. Under CMP conditions tellurium may tend to migrate andagglomerate on the surface of the wafer during planarization. This leadsto films with non-homogenous compositions and surface characteristicsthat vary from one location to another across the wafer.

One polishing composition for polishing substrates having a chalcogenidephase change material is disclosed in United States Patent ApplicationPublication No. 20070178700 to Dysard et al. Dysard et al. disclose achemical mechanical polishing composition for polishing a phase changealloy containing substrate, the composition comprising: (a) aparticulate abrasive material in an amount of not more than about 3percent by weight; (b) at least one chelating agent capable of chelatingthe phase change alloy, a component thereof, or a substance formed fromthe phase change alloy material during chemical mechanical polishing;and (c) an aqueous carrier therefor.

There remains an ongoing need to develop new chemical mechanicalpolishing (CMP) compositions capable of selectively removing phasechange materials with high removal rates, while also providing reducedtotal defects and Te residue defects.

The present invention provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises a germanium-antimony-tellurium phase change alloy;providing a chemical mechanical polishing composition, wherein thechemical mechanical polishing composition comprises (consistsessentially of), as initial components: water; 0.1 to 5 wt % of anabrasive; 0.001 to 5 wt % of at least one of a phthalic acid, a phthalicanhydride, a phthalate compound and a phthalic acid derivative; 0.001 to5 wt % of a chelating agent; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent; wherein thechemical mechanical polishing composition has a pH 7.1 to 12; providinga chemical mechanical polishing pad; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the chemical mechanical polishing pad at or near the interfacebetween the chemical mechanical polishing pad and the substrate; whereinat least some of the germanium-antimony-tellurium phase change alloy isremoved from the substrate.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises a germanium-antimony-tellurium phase change alloy;providing a chemical mechanical polishing composition, wherein thechemical mechanical polishing composition comprises (consistsessentially of), as initial components: water; 0.1 to 5 wt % of anabrasive; 0.001 to 5 wt % of at least one of a phthalic acid, a phthalicanhydride, a phthalate compound and a phthalic acid derivative; 0.001 to5 wt % of a chelating agent; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent; wherein thechemical mechanical polishing composition has a pH 7.1 to 12; providinga chemical mechanical polishing pad; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the chemical mechanical polishing pad at or near the interfacebetween the chemical mechanical polishing pad and the substrate; whereinat least some of the germanium-antimony-tellurium phase change alloy isremoved from the substrate; wherein the abrasive is a colloidal silicaabrasive having an average particle size of 110 to 130 inn; wherein theoxidizing agent is hydrogen peroxide; wherein the chelating agent isselected from ethylene diamine tetra acetic acid and salts thereof; andwherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy removal rate of ≧1,000Å/min with a platen speed of 60 revolutions per minute, a carrier speedof 55 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 200 ml/min, and a nominal down force of 8.27kPa (1.2 psi) on a 200 mm polishing machine where the chemicalmechanical polishing pad comprises a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises a germanium-antimony-tellurium phase change alloy;providing a chemical mechanical polishing composition, wherein thechemical mechanical polishing composition comprises (consistsessentially of), as initial components: water; 0.1 to 5 wt % of anabrasive; 0.001 to 5 wt % of at least one of a phthalic acid, a phthalicanhydride, a phthalate compound and a phthalic acid derivative; 0.001 to5 wt % of a chelating agent; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent; wherein thechemical mechanical polishing composition has a pH 7.1 to 12; providinga chemical mechanical polishing pad; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the chemical mechanical polishing pad at or near the interfacebetween the chemical mechanical polishing pad and the substrate; whereinat least some of the germanium-antimony-tellurium phase change alloy isremoved from the substrate; wherein the abrasive is a colloidal silicaabrasive having an average particle size of 110 to 130 nm; wherein theoxidizing agent is hydrogen peroxide; wherein the chelating agent isselected from ethylene diamine tetra acetic acid and salts thereof;wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy removal rate of ≧1,000Å/min with a platen speed of 60 revolutions per minute, a carrier speedof 55 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 200 ml/min, and a nominal down force of 8.27kPa (1.2 psi) on a 200 mm polishing machine where the chemicalmechanical polishing pad comprises a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad; and, wherein the chemical mechanicalpolishing composition facilitates the germanium-antimony-tellurium phasechange alloy removal rate of ≧1,000 Å/min with a post polish SP1 defectcount (>0.16 μm) of ≦200.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises a germanium-antimony-tellurium phase change alloy;providing a chemical mechanical polishing composition, wherein thechemical mechanical polishing composition comprises (consistsessentially of), as initial components: water; 0.1 to 5 wt % of anabrasive; 0.001 to 5 wt % of at least one of a phthalic acid, a phthalicanhydride, a phthalate compound and a phthalic acid derivative; 0.001 to5 wt % of a chelating agent; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent; wherein thechemical mechanical polishing composition has a pH 7.1 to 12; providinga chemical mechanical polishing pad; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the chemical mechanical polishing pad at or near the interfacebetween the chemical mechanical polishing pad and the substrate; whereinat least some of the germanium-antimony-tellurium phase change alloy isremoved from the substrate; wherein the abrasive is a colloidal silicaabrasive having an average particle size of 110 to 130 nm; wherein theoxidizing agent is hydrogen peroxide; wherein the chelating agent isselected from ethylene diamine tetra acetic acid and salts thereof;wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy removal rate of ≧1,000Å/min with a platen speed of 60 revolutions per minute, a carrier speedof 55 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 200 ml/min, and a nominal down force of 8.27kPa (1.2 psi) on a 200 mm polishing machine where the chemicalmechanical polishing pad comprises a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad; wherein the chemical mechanical polishingcomposition facilitates the germanium-antimony-tellurium phase changealloy removal rate of ≧1,000 Å/min with a post polish SP1 defect count(>0.16 μm) of ≦200; and, wherein ≦175 of the post polishing SP1 defectsare tellurium residue defects.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises a germanium-antimony-tellurium phase change alloy;providing a chemical mechanical polishing composition, wherein thechemical mechanical polishing composition comprises (consistsessentially of), as initial components: water; 0.1 to 5 wt % of anabrasive; 0.001 to 5 wt % of at least one of a phthalic acid, a phthalicanhydride, a phthalate compound and a phthalic acid derivative; 0.001 to5 wt % of a chelating agent; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent; wherein thechemical mechanical polishing composition has a pH 7.1 to 12; providinga chemical mechanical polishing pad; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the chemical mechanical polishing pad at or near the interfacebetween the chemical mechanical polishing pad and the substrate; whereinat least some of the germanium-antimony-tellurium phase change alloy isremoved from the substrate; wherein the abrasive is a colloidal silicaabrasive having an average particle size of 110 to 130 nm; wherein theoxidizing agent is hydrogen peroxide; wherein the chelating agent isselected from ethylene diamine tetra acetic acid and salts thereof;wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy removal rate of ≧1,000Å/min with a platen speed of 60 revolutions per minute, a carrier speedof 55 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 200 ml/min, and a nominal down force of 8.27kPa (1.2 psi) on a 200 mm polishing machine where the chemicalmechanical polishing pad comprises a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad; wherein the chemical mechanical polishingcomposition facilitates the germanium-antimony-tellurium phase changealloy removal rate of ≧1,000 Å/min with a post polish SP1 defect count(>0.16 μm) of ≦200; wherein ≦175 of the post polishing SP1 defects aretellurium residue defects; wherein the substrate further comprisesSi₃N₄; wherein at least some of the Si₃N₄ is removed from the substrate;and wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy to Si₃N₄ removal rateselectivity of ≧15:1.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises a germanium-antimony-tellurium phase change alloy;providing a chemical mechanical polishing composition, wherein thechemical mechanical polishing composition comprises (consistsessentially of), as initial components: water; 0.1 to 5 wt % of anabrasive; 0.001 to 5 wt % of at least one of a phthalic acid, a phthalicanhydride, a phthalate compound and a phthalic acid derivative; 0.001 to5 wt % of a chelating agent; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent; wherein thechemical mechanical polishing composition has a pH 7.1 to 12; providinga chemical mechanical polishing pad; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the chemical mechanical polishing pad at or near the interfacebetween the chemical mechanical polishing pad and the substrate; whereinat least some of the germanium-antimony-tellurium phase change alloy isremoved from the substrate; wherein the abrasive is a colloidal silicaabrasive having an average particle size of 110 to 130 nm; wherein theoxidizing agent is hydrogen peroxide; wherein the chelating agent isselected from ethylene diamine tetra acetic acid and salts thereof;wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy removal rate of ≧1,000Å/min with a platen speed of 60 revolutions per minute, a carrier speedof 55 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 200 ml/min, and a nominal down force of 8.27kPa (1.2 psi) on a 200 mm polishing machine where the chemicalmechanical polishing pad comprises a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad; wherein the chemical mechanical polishingcomposition facilitates the germanium-antimony-tellurium phase changealloy removal rate of ≧1,000 Å/min with a post polish SP1 defect count(>0.16 μm) of ≦200; wherein ≦175 of the post polishing SP1 defects aretellurium residue defects; wherein the substrate further comprisestetraethyl orthosilicate (TEOS); wherein at least some of the TEOS isremoved from the substrate; and, wherein the chemical mechanicalpolishing composition exhibits a germanium-antimony-tellurium phasechange alloy to TEOS removal rate selectivity of ≧15:1.

DETAILED DESCRIPTION

The chemical mechanical polishing method of the present invention isuseful for polishing a substrate containing a chalcogenide phase changealloy. The chemical mechanical polishing composition used in the methodof the present invention provides a high chalcogenide phase change alloyremoval rate with favorable selectivity over additional materials on thesubstrate and with low total defects and low Te residue defects.

Substrates suitable for use in the method of the present invention forchemical mechanical polishing comprise a germanium-antimony-tellurium(GST) phase change alloy.

Substrates suitable for use in the method of the present invention forchemical mechanical polishing optionally further comprise an additionalmaterial selected from phosphor silicate glass (PSG), boro-phosphorsilicate glass (BPSG), undoped silicate glass (USG), spin-on-glass(SOG), tetraethyl orthosilicate (TEOS), plasma-enhanced TEOS (PETEOS),flowable oxide (FOx), high-density plasma chemical vapor deposition(HDP-CVD) oxide, and silicon nitride (e.g., Si₃N₄). Preferably, thesubstrate further comprises an additional material selected from Si₃N₄and TEOS.

Abrasives suitable for use in the chemical mechanical polishingcomposition used in the chemical mechanical polishing method of thepresent invention include, for example, inorganic oxides, inorganichydroxides, inorganic hydroxide oxides, metal borides, metal carbides,metal nitrides, polymer particles and mixtures comprising at least oneof the foregoing. Suitable inorganic oxides include, for example, silica(SiO₂), alumina (Al₂O₃), zirconia (ZrO₂), ceria (CeO₂), manganese oxide(MnO₂), titanium oxide (TiO₂) or combinations comprising at least one ofthe foregoing oxides. Modified forms of these inorganic oxides, such as,organic polymer-coated inorganic oxide particles and inorganic coatedparticles can also be utilized if desired. Suitable metal carbides,boride and nitrides include, for example, silicon carbide, siliconnitride, silicon carbonitride (SiCN), boron carbide, tungsten carbide,zirconium carbide, aluminum boride, tantalum carbide, titanium carbide,or combinations comprising at least one of the foregoing metal carbides,boride and nitrides. Preferably, the abrasive used is a colloidal silicaabrasive. More preferably, the abrasive used is a colloidal silicahaving an average particle size of 1 to 200 nm (more preferably 100 to150 nm, most preferably 110 to 130 nm) as determined by well known laserlight scattering techniques.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention preferablycomprises, as an initial component, 0.1 to 5 wt %, more preferably 0.5to 3 wt %, still more preferably 1 to 3 wt %, yet still more preferably1.5 to 2.5 wt % abrasive. Preferably, the abrasive is a colloidal silicaabrasive. Most preferably, the chemical mechanical polishing compositionof the present invention comprises, as an initial component, 1.5 to 2.5wt % of a colloidal silica abrasive having an average particle size of110 to 130 nm.

Preferably, the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention comprises,as an initial component, 0.001 to 5 wt % (more preferably 0.05 to 5 wt%, still more preferably 0.1 to 4 wt %, most preferably 0.2 to 0.4 wt %)of at least one of a phthalic acid, a phthalic anhydride, a phthalatecompound and a phthalic acid derivative. Preferably, phthalic acid isincorporated into the chemical mechanical polishing composition usedthrough the addition of a phthalate compound such as for example,hydrogen potassium phthalate; or through the addition of a phthalic acidderivative such as, for example, ammonium hydrogen phthalate. Mostpreferably, the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention comprises,as an initial component, 0.2 to 0.4 wt % of ammonium hydrogen phthalate.

Preferably, the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention comprises,as an initial component, 0.001 to 5 wt % (more preferably 0.01 to 5 wt%, still more preferably 0.15 to 0.25 wt %) of a chelating agent.Preferably, wherein the chelating agent is selected from ethylenediamine tetra acetic acid (EDTA), analogs and salts thereof. Preferredanalogs of EDTA include nitrilotriacetic acid (NTA); ethylene glycoltetra acetic acid (EGTA); 1,2-cyclohexanediaminetetraacetic acid(CyDTA); hexamethylene diamine tetra acetic acid (HDTA);1,2-diaminopropane-N,N,N′,N′-tetraacetic acid (Methyl-EDTA);1,3-diamino-2-propanol-N,N,N′,N′-tetraacetic acid (DPTA-OH);diethylenetriaminepentaacetic acid (DTPA);N-(2-hydroxyethyl)ethylenediamine-N,N,N′,N′-triacetic acid (HEDTA);triethylenetetramine-N,N,N′,N″,N′″,N′″-hexaacetic acid (TTHA); and saltsthereof. More preferably, wherein the chelating agent is selected fromethylene diamine tetra acetic acid and salts thereof. Most preferably,wherein the chemical mechanical polishing composition used comprises, asan initial component, 0.15 to 0.25 wt % of a chelating agent, whereinthe chelating agent is selected from ethylene diamine tetra acetic acidand salts thereof (e.g., ethylene diamine tetra acetic acid dipotassiumsalt dihydrate).

Preferably, the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention comprises,as an initial component, 0.001 to 0.1 wt % (more preferably 0.01 to 0.1wt %, more preferably 0.04 to 0.06 wt %) of a poly(acrylicacid-co-maleic acid). Still more preferably, the chemical mechanicalpolishing composition used in the chemical mechanical polishing methodof the present invention comprises, as an initial component, 0.001 to0.1 wt % (yet more preferably 0.01 to 0.1 wt %, most preferably 0.04 to0.06 wt %) of a poly(acrylic acid-co-maleic acid), wherein thepoly(acrylic acid-co-maleic acid) has a weight average molecular weightof 2,500 to 10,000 (preferably 2,500 to 5,000; most preferably 2,500 to3,500).

Preferably, the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention comprises,as an initial component, 0.001 to 3 wt % (more preferably 0.01 to 3 wt%, still more preferably 0.05 to 0.15 wt %) of an oxidizing agent.Preferably, the oxidizing agent is hydrogen peroxide. Most preferably,the chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention comprises, as aninitial component, 0.05 to 0.15 wt % of hydrogen peroxide.

Preferably, the water used in the chemical mechanical polishingcomposition used in the chemical mechanical polishing method of thepresent invention is at least one of deionized and distilled to limitincidental impurities.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention optionally furthercomprises additional additives selected from pH adjusters, dispersants,surfactants, buffers and biocides.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention preferably has a pHof 7.1 to 12 (preferably 7.5 to 10, more preferably 7.5 to 9, mostpreferably 7.5 to 8.5). Acids suitable for adjusting the pH of thechemical mechanical polishing composition include, for example, nitricacid, sulfuric acid and hydrochloric acid. Bases suitable for adjustingthe pH of the chemical mechanical polishing composition include, forexample, ammonium hydroxide, potassium hydroxide, tetramethylammoniumhydroxide and bicarbonate; preferably tetramethylammonium hydroxide.

Optionally, in the chemical mechanical polishing method of the presentinvention, the substrate further comprises Si₃N₄; wherein at least someof the Si₃N₄ is removed from the substrate; and, wherein the chemicalmechanical polishing composition used exhibits agermanium-antimony-tellurium phase change alloy to Si₃N₄ removal rateselectivity of ≧10:1 (more preferably ≧15:1; most preferably ≧18:1).

Optionally, in the chemical mechanical polishing method of the presentinvention, the substrate further comprises tetraethyl orthosilicate(TEOS); wherein at least some of the TEOS is removed from the substrateand wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy to TEOS removal rateselectivity of ≧10:1 (preferably ≧15:1; more preferably ≧16:1).

Preferably, the chemical mechanical polishing method of the presentinvention, comprises: providing a substrate, wherein the substratecomprises a germanium-antimony-tellurium phase change alloy; providing achemical mechanical polishing composition, wherein the chemicalmechanical polishing composition comprises (consists essentially of), asinitial components: water; 0.1 to 5 wt % (preferably 0.5 to 3 wt %, morepreferably 1 to 3 wt %, most preferably 1.5 to 2.5 wt %) of an abrasive(preferably, wherein the abrasive is a colloidal silica abrasive, morepreferably, a colloidal silica abrasive having an average particle sizeof 1 to 200 nm, yet more preferably 100 to 150 nm, most preferably 110to 130 nm); 0.001 to 5 wt % (preferably 0.05 to 5 wt %, more preferably0.1 to 4 wt %, most preferably 0.2 to 0.4 wt %) of at least one of aphthalic acid, a phthalic anhydride, a phthalate compound and a phthalicacid derivative (preferably ammonium hydrogen phthalate); 0.001 to 5 wt% (preferably 0.01 to 5 wt %, more preferably 0.15 to 0.25 wt %) of achelating agent (preferably, wherein the chelating agent is selectedfrom ethylene diamine tetra acetic acid and salts thereof); 0.001 to 0.1wt % (preferably 0.01 to 0.1 wt %, more preferably 0.04 to 0.06 wt %) ofa poly(acrylic acid-co-maleic acid); 0.001 to 3 wt % (preferably 0.01 to3 wt %, more preferably 0.05 to 0.15 wt %) of an oxidizing agent(preferably, wherein the oxidizing agent is hydrogen peroxide); whereinthe chemical mechanical polishing composition has a pH 7.1 to 12(preferably 7.5 to 10, more preferably 7.5 to 9, most preferably 7.5 to8.5); providing a chemical mechanical polishing pad; creating dynamiccontact at an interface between the chemical mechanical polishing padand the substrate; and dispensing the chemical mechanical polishingcomposition onto the chemical mechanical polishing pad at or near theinterface between the chemical mechanical polishing pad and thesubstrate; wherein at least some of the germanium-antimony-telluriumphase change alloy is removed from the substrate; wherein the chemicalmechanical polishing composition exhibits a germanium-antimony-telluriumphase change alloy removal rate of ≧1,000 Å/min with a platen speed of60 revolutions per minute, a carrier speed of 55 revolutions per minute,a chemical mechanical polishing composition flow rate of 200 ml/min, anda nominal down force of 8.27 kPa (1.2 psi) on a 200 mm polishing machinewhere the chemical mechanical polishing pad comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad; wherein the chemicalmechanical polishing composition facilitates thegermanium-antimony-tellurium phase change alloy removal rate of ≧1,000Å/min with a post polish SP1 defect count (>0.16 μm) of ≦200 (morepreferably 0 to 200; most preferably 0 to 190); wherein ≦175 (morepreferably 0 to 170; most preferably 0 to 165) of the post polishing SP1defects are tellurium residue defects; optionally, wherein the substratefurther comprises Si₃N₄, wherein at least some of the Si₃N₄ is removedfrom the substrate and wherein the chemical mechanical polishingcomposition exhibits a germanium-antimony-tellurium phase change alloyto Si₃N₄ removal rate selectivity of ≧15:1 (preferably ≧18:1); and,optionally, wherein the substrate further comprises tetraethylorthosilicate (TEOS), wherein at least some of the TEOS is removed fromthe substrate and wherein the chemical mechanical polishing compositionexhibits a germanium-antimony-tellurium phase change alloy to TEOSremoval rate selectivity of ≧15:1 (preferably ≧16:1).

Some embodiments of the present invention will now be described indetail in the following Examples.

EXAMPLES Chemical Mechanical Polishing Compositions

The chemical mechanical polishing compositions (CMPC's) tested aredescribed in Table 1. The chemical mechanical polishing compositions A-Dare comparative formulations, which are not within the scope of theclaimed invention.

TABLE 1 Poly(acrylic- AHP* EDTA^(£) co-maleic acid)^(ζ) abrasive^(††)H₂O₂ HClO₄ CMPC (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) pH^(α) 1 0.30.2 0.05 2 0.1 — 8 A — — — 3.5 — — 8 B 0.3 0.2 — 2 0.1 — 8 C — 0.2 0.052 0.1 — 8 D 0.3 — — 2.5 — 0.2 8 *Ammonium hydrogen phosphate^(£)ethylene diamine tetra acetic acid dipotassium salt dihydrate ^(ζ)A50 wt % solution in water of a poly(acrylic acid-co-maleic acid) havinga weight average molecular weight of 3,000 from Aldrich Chemicals^(††)Klebosol ® K1630 colloidal silica having an average particle sizeof 120 nm manufactured by AZ Electronic Materials and commerciallyavailable from Rohm and Haas Electronic Materials CMP Inc. ^(α)Adjustedthrough the addition of tetramethylammonium hydroxide

Polishing Tests

Polishing experiments were performed on germanium-antimony-tellurium(GST) blanket wafers (Si/1 kÅ thermal oxide/200 Å TiN/1500 Å GST film)from SKW Associates Inc. using the chemical mechanical polishingcompositions described in Table 1. The polishing experiments wereperformed using an Applied Materials, Inc. Mirra® 200 mm polishingmachine equipped with an ISRM detector system using an IC1010™polyurethane polishing pad (commercially available from Rohm and HaasElectronic Materials CMP Inc.) under a 1.2 psi (8.27 kPa) down force, achemical mechanical polishing composition flow rate of 200 ml/min, aplaten speed of 60 rpm and a carrier speed of 55 rpm. A Diagrid®AD3BG-150855 diamond pad conditioner (commercially available from KinikCompany) was used to condition the polishing pad. The polishing pad wasbroken in with the conditioner using a down force of 14.0 lbs (6.35 kg)for 20 minutes then with a down force of 9.0 lbs (4.08 kg) for 10minutes before polishing. The polishing pad was further conditioned insitu during wafer polishing using a down force of 9.0 lbs (4.08 kg). TheGST removal rate data reported in Table 2 was determined using a JordanValley JVX-5200T metrology tool. Si₃N₄ and TEOS blanket wafers from SVTCand Advantiv respectively were also polished under the noted conditions.The Si₃N₄ and TEOS removal rates reported in Table 2 were determined bymeasuring the film thickness before and after polishing using aKLA-Tencor FX200 metrology tool. The defect count analysis fordefects >0.16 μm was performed using SP1 metrology tool from KLA-Tencor.A given number (noted in TABLE 2) of randomly selected defects werereviewed using SEM EDR5200 metrology tool from KLA-Tencor to identify Teresidue defects. The findings were then extrapolated for the remainderof the defects to estimate the total number of Te residue defects. Theresults of the polishing tests are presented in Table 2.

TABLE 2 GST TEOS Si₃N₄ removal removal removal SEM Te rate rate rateTotal reviewed Residue CMPC (Å/min) (Å/min) (Å/min) Defect^(†) DefectsDefects 1 1045 65 57 188 50 165 A 204 85 58 806 100 467 B 938 74 55 31250 218 C 149 40 36 1412 50 0 D 856 79 88 939 100 667 ^(†)Total defectshaving a size >0.16 μm.

We claim:
 1. A method for chemical mechanical polishing of a substrate,comprising: providing a substrate, wherein the substrate comprises agermanium-antimony-tellurium phase change alloy; providing a chemicalmechanical polishing composition, wherein the chemical mechanicalpolishing composition comprises, as initial components: water; 0.1 to 5wt % of an abrasive, wherein the abrasive is a colloidal silica abrasivehaving an average article size of 110 to 130 nm; 0.001 to 5 wt % of atleast one of a phthalic acid, a phthalic anhydride, a phthalate compoundand a phthalic acid derivative; 0.001 to 5 wt % of a chelating agent,wherein the chelating agent is selected from ethylene diamine tetraacetic acid ad salts thereof; 0.001 to 0.1 wt % of a poly(acrylicacid-co-maleic acid); 0.001 to 3 wt % of an oxidizing agent, wherein theoxidizing agent is hydrogen peroxide; wherein the chemical mechanicalpolishing composition has a pH 7.1 to 12; providing a chemicalmechanical polishing pad; creating dynamic contact at an interfacebetween the chemical mechanical polishing pad and the substrate; anddispensing the chemical mechanical polishing composition onto thechemical mechanical polishing pad at or near the interface between thechemical mechanical polishing pad and the substrate; wherein at leastsome of the germanium-antimony-tellurium phase change alloy is removedfrom the substrate; wherein the chemical mechanical polishingcomposition exhibits a germanium-antimony-tellurium phase change alloyremoval rate of at least 1,000 Å/min with a platen speed of 60revoluions per minute, a carrier speed of 55 revolutions per minute, achemical mechanical polishing composition flow rate of 200 ml/min, and anominal down force of 8.27 kPa (1.2 psi) on a 200 mm polishing machinewhere the chemical mechanical polishing pad comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad; and, wherein the chemicalmechanical polishing composition facilitates thegermanium-antimony-tellurium phase change alloy removal rate of at least1,000 Å/min with a post polish SP1 defect count (>0.16 μm of no morethan
 200. 2. The method of claim 1, wherein the substrate furthercomprises Si₃N₄; wherein at least some of the Si₃N₄ is removed from thesubstrate; and, wherein the chemical mechanical polishing compositionexhibits a germanium-antimony-tellurium phase change alloy to Si₃N₄removal rate selectivity of ≧10:1.
 3. The method of claim 1, wherein thesubstrate further comprises tetraethyl orthosilicate (TEOS); wherein atleast some of the TEOS is removed from the substrate and wherein thechemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy to TEOS removal rateselectivity of ≧10:1.
 4. The method of claim 1, wherein the substratefurther comprises Si₃N₄; wherein at least some of the Si₃N₄ is removedfrom the substrate; and wherein the chemical mechanical polishingcomposition exhibits a germanium-antimony-tellurium phase change alloyto Si₃N₄ removal rate selectivity of ≧15:1.
 5. The method of claim 1,wherein the substrate further comprises tetraethyl orthosilicate (TEOS);wherein at least some of the TEOS is removed from the substrate; and,wherein the chemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy to TEOS removal rateselectivity of ≧15:1.
 6. The method of claim 1, wherein ≦175 of the postpolishing SP1 defects are tellurium residue defects.
 7. The method ofclaim 6, wherein the substrate further comprises Si₃N₄; wherein at leastsome of the Si₃N₄ is removed from the substrate; and wherein thechemical mechanical polishing composition exhibits agermanium-antimony-tellurium phase change alloy to Si₃N₄ removal rateselectivity of ≧15:1.
 8. The method of claim 6, wherein the substratefurther comprises tetraethyl orthosilicate (TEOS); wherein at least someof the TEOS is removed from the substrate; and, wherein the chemicalmechanical polishing composition exhibits a germanium-antimony-telluriumphase change alloy to TEOS removal rate selectivity of ≧15:1.